Methods for evaluation of nutritional status of fish larvae

Methods for evaluation of nutritional status of fish larvae

Desde 1990-01-01
hasta 1993-01-01

Detalles del proyecto

Coste total:

No disponible

Aportación de la UE:

No disponible

Coordinado en:

Denmark

Objetivo

The aim of the project is to achieve new knowledge on the biochemical and physiological effects of starvation in turbot larvae by simultaneous measurements of parameters known to be affected by starvation. Based on the achieved knowledge, guidelines on the practical use of these parameters as indicators of malnutrition in aquaculture, larval fish ecology etc. will be established. Various indicators of nutritional status have been compared in feeding and starving turbot larvae reared in large outdoor tanks and in laboratory systems. The study included whole larvae parameters such as length, dry weight and relative condition. Organ related parameters included otolith diameter and intestinal histology and biochemical parameters involved measurement of fatty acids, ascorbic acid, ribonucleic acid (RNA), deoxyribonucleic acid (DNA), total protein and free amino acids.

The biochemical composition of the larvae at hatching seemed to be dependent on maternal nutrition. During yolk sac absorption the larvae showed a decrease in the lipids content and an increase in the protein content. After day 8 the influence of food became visible.

Comparisons of feeding and starving larvae from the same readings showed that most of the investigated parameters were affected by starvation, but generally the natural variations between readings were higher than the effects of starvation. Only the parameters lipid droplets in intestinal cells, relative condition and relative otolith diameter seemed to be associated with starvation in fish larvae.

After onset of starvation, lipid droplets disappeared within 24 h, relative condition decreased by approximately 5% per day and relative otolith diameter increased by about 5% per day. The slowest growing among feeding larvae showed no reduction in relative condition, but an increased relative otolith diameter.Turbot larvae will be reared under standard laboratory conditions based on Brachionus/Artemia in Vigo, Spain and under extensive conditions in Hirtshals, Denmark. (Under laboratory conditions it is possible to handle high numbers of larvae, and starvation is easily induced. However, laboratory reared larvae are usually in a poorer health condition with slower growth and high mortality. Extensively produced larvae have high growth rates and low mortality. However, production capacity is limited, and transfer to starvation may affect the larvae).

Larvae with an age of 3 days, (end of yolk sac stage), 10 days (critical age in rearing) and 17 days (end of critical age) are deprived of food. At selected time intervals after onset of starvation, samples of larvae are analysed and compared to fed larvae. The parameters considered for the comparative study will be the following: length, dry weight, growth rate, condition factor, mortality, intestinal histology, lipids, vitamin C, RNA/DNA, CHN, amino acid profile.